Synapse development will be studied in cloned cell lines of nerve and muscle. A number of clonal cell lines of muscle have been shown to form cholinergic synapses with spinal cord neurons. This system will be characterized as a step in the development of an all clonal system. A collection of new cell lines has been established. These cells have been cloned and characterized and have many of the electrical, pharmacological and biochemical properties of nerve, muscle and glia. Five new neuronal cell lines will be screened for their ability to form chemical synapses. The C1300 neuroblastoma does not innervate myotubes in culture. The trophic interactions involved in innervation will be studied utilizing cloned lines as well as disaggregated spinal cord cells. Muscle development and innervation will be studied in rat diaphragm in vivo and organ culture. BIBLIOGRAPHIC REFERENCES: Steinbach, J.H., and S.F. Heinemann. Nerve-Muscle Interaction in Clonal Cell Culture. In Exploratory Concepts in Muscular Dystrophy 11, pp. 161-169 1975). Klier, G., D. Schubert, and S.F. Heinemann. Ultrastructural Changes Accompanying the Induced Differentiation of Clonal Rat Nerve and Glia. Neurobiology, 5, 1 (1975).